Thanks for coming back, @Muz123. 

Based on your "VAT" term, it looks like you're using the UK or our international versions in QuickBooks Online (QBO). I've got the two options to hide the VAT Registration Form column in the purchase order. 

If you're referring to the VAT column on the middle part of the transaction, let's go back to the Content tab to hide it. I'll guide you how. 

1. Select the Gear icon at the upper right and choose Custom form styles.
2. Locate the Master template and click Edit. 
3. Go to the Content tab. 
4. Click the middle part of the purchase order. 
5. Uncheck the VAT box. 
6. Choose Done.

The screenshot below shows you the last four steps. 

Here's a sample screenshot of the result: 

If you're referring to the VAT Registration No. on the transaction's header, I'd suggest selecting No VAT in the Amounts are field. This way, you can hide it (see the first screenshot below). Before that, I recommend consulting your tax advisor/accountant to check if the PO isn't taxable or not to ensure your books are accurate. If taxable, there isn't a way to remove it. The second screenshot below displays the result. 

Lastly, I recommend running the reports below to help you efficiently manage your purchase orders in QBO: 

• Open Purchase Order List
• Open Purchase Order Detail
• Purchases by Product/Service Detail
• Purchases by Vendor/Supplier Detail

The Community and I will be around to help if you have other concerns. Take care always.